Electronic tremolo effect producing device

ABSTRACT

An electronic tremolo effect producing device in which a musical sound signal frequency is deviated by as much as frequencies of two signals having different frequencies each sufficiently lower than that of said musical sound signal by means of two frequency deviation devices. Respectively a part of the output signal of each frequency deviation device mentioned above is fed back to an input side of its own frequency deviation device or the other frequency deviation device thereby to obtain a multiple spectrum signal and this signal is mixed with an original musical sound signal thereby to produce a tremolo effect sound.

United States Patent Uchiyama [54] ELECTRONIC TREMOLO EFFECT PRODUCINGDEVICE [72] Inventor: Yasuji Uchiyama, Shizuoka, Japan [73] Assignee:Nippon Gakki Seizo Kabushiki Kaisha, Shizuoka-ken, Japan [22] Filed:Jan. 25, 1971 [21] Appl. No.1 109,440

[30] Foreign Application Priority Data 1 5] Oct. 24, 1972 PrimaryExaminer-Lewis H. Myers Assistant Examiner- U. Weldon Attorney-Holman &Stern [57] ABSTRACT An electronic tremolo effect producing device inJan. 26, 1970 Japan ..45/6274 which a musical sound signal frequency isdeviated by Jan. 26, 1970 Japan ..45/7206 as much as frequencies of twosignals having different frequencies each sufficiently lower'than thatof said LS. Cl 1, 4 musical ound signal by mgans of two frequency CL...G10h deviation devices Respective a of the output [58] Fleld of Search..84/1.01, 1.24, 1.25 Signal of each frequency deviation devicementioned I above is fed back to an input side of its own frequency [56] Referencas Clted deviation device or the other frequency deviationUNITED STATES PATENTS device thereby to obtain a multiple spectrumsignal and this signal 18 mixed with an original musical sound aayne isignal thereby to produce a tremolo effect sound. ayne 2,916,706 12/1959Timperman ..84/ 1.24 X 1 Claim, 5 Drawing Figures FREQUENCY MUS|CALDEVIATION R3 souuo DEVICE MM SIGNAL 1 CIRCUIT 'Q a u l a a i k R4 MS I+Af| W e 9 Fe m 1 E F EED BACK F BI e DEVICE FEED-BACK R2 R5 WW DEVICE 2FREQUENCY DEVIATION DEVICE FIG. I

FREQUENCY MUSICAL DEVIATION SOLND DEVIC R3 SIGNAL WW CIBCUIT SI MS g +AfMM FBI FEED-BACK DEVICE R5 F52 FREQUENCY DEv|AT|ON DEVICE PHASE F G. 2

SEPARATOR b PS MI F U) C MODULATOR HLTER EXTREMELY Low MODULATORFREQUENCY OSCILLATOR LEVEL FREQUENCY PATENTEDum 24 I972 MUSICAL SOUNDSIGNAL CIRCUIT SHEET 2 BF 2 FIG.4

DEVIATION DEVICE FREQUENCY FBI FEEa AcK I FS FR 2 DE FIG.5

DEVI

s WW DEVICE EQUENCY VIATION Af l Af l

Afl

Afl

FREQUENCY ELECTRONIC TREMOLO EFFECT PRODUCING DEVICE BACKGROUND OF THEINVENTION This invention relates generally to an electronic tremoloeffect producing device and more particularly to a type of device forcreating tremolo effect sounds in a purely electronic manner.

Heretofore, there have been used tremolo or chorus producing deviceswherein an electrical musical sound signal (as carrier wave) isamplitude-modulated with a signal (.as a modulating wave) having adesired frequency and waveform, or as an alternative method, anelectrical signal is converted into a sound signal through a loudspeakerrotating at a desired speed. (Hereinafter as far as an electric musicalinstrument is concerned a tremolo effect represents a modulation by afrequency ranging from 5 Hz to Hz, while a chorus effect represents amodulation by a frequency ranging from 0.5 Hz to 2 Hz.). However, in thefirst mentioned system, since only amplitude modulation is employed, thefrequency of the musical sound signal remains unchanged and thereforethe resultant sound is rather monotonous and the sound effect is verypoor. On the other hand, in the second system, the Doppler effect isproduced in the musical signal by the rotation of loudspeaker, and as aresult the frequency and phase of the musical sound signal are variedand the-signal level is also varied with the variation of directivitywhereby a wide spread sensation can be obtained. The second system isvery effective, but however involves disadvantages such as anexcessively complicated rotating mechanism and driving mechanism of theloudspeaker and a high production cost thereof. Furthermore, there arepossibilities of various undesirable noises such as wind noise and othermechanical noises being introduced into the output at the time ofrotation of the loudspeaker.

SUMMARY OF THE INVENTION It is accordingly a primary object of thepresent invention to provide a novel organization of a tremolo or choruseffect producing device wherein all of the above-described drawbacks ofthe conventional devices can be eliminated.

Another object of the present invention is to provide a tremolo effectproducing device wherein a tremolo effect which is very effective andrich in natural sound sensation can be obtained in a purely electronicmanner.

A further object of the present invention is to provide a tremolo effectproducing device which simulates substantially a multi-rank soundsource.

A still further object of the present invention is to provide a tremoloeffect producing device wherein a tremolo effect sound can be producedor stopped at an instant.

More specifically, it is an object of the present invention to provide anovel tremolo or chorus effect producing device which can operate in apurely electronic manner and is simple in organization and economical inproduction.

The nature, utility and the principle of the invention will be moreclearly understood from the following detailed description withreference to the accompanying drawings.

2 BRIEF DESCRIPTION OF THE INVENTION In the accompanying drawings:

FIG. 1 is a block diagram illustrating a principle of the tremolo effectproducing device according to the present invention;

FIG. 2 is a block diagram showing an example of the frequency deviationdevice included in FIG. 1;

FIG. 3 exhibits an example of the frequency spectrum of a signalobtained in the tremolo effect producing device'according to the presentinvention;

FIG. 4 is a block diagram of another embodiment of the tremolo effectproducing device according to the present invention; and

FIG. 5 illustrates a frequency spectrum of a signal obtained in thetremolo effect producing device shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION With reference now to FIG. 1 whichis aschematic block diagram illustrating an example of the electronictremolo effect producing device according to the present invention,reference symbol MS represents a musical sound signal circuit adapted togenerate a musical sound signal (the signal usually comprises aplurality of frequency components thus constituting a frequency spectrumband and the fundamental frequency thereof is varied in accordance withthe progression of the musical performance, but for convenience inexplanation in this specification, the musical signal is represented byonly a single frequency off Hz) and frequency deviation devices FS, andPS serve to deviate the frequency (j) of the musical sound signal by asmuch as a frequency (approximately 0.5 10 Hz) of Af and of Afrespectively, both of which are sufficiently lower than the frequency(f). The positive sign of +Af means that the frequency (f) is deviatedhigher by as much as Af while, in the same way, the negative sign(-) ofAf means that the frequency (j) is deviated lower by as much as AfReference symbols FB and FB represent feed-back devices. The feedbackdevice FB is connected between an output terminal k of the frequencydeviation device PS and an input terminal j of the frequency deviationdevice F8 while the feed-back device FB is connected between an outputterminal I of the frequency deviation device F8 and an input terminal iof the frequency deviation device PS The feed-back devices FB and FB maybe of a well known type, and can have a desired frequencycharacteristic. Reference symbols R through R are resistors for mixingof signals.

In FIG. 2 which exhibits a schematic block diagram of an example of thefrequency deviation device shown in FIG. 11, the frequency deviationdevice comprises; a phase separator PS which is adapted to convert aninput signal into two output signals which are different in phase fromeach other; an extremely low frequency oscillator LFO whichsimultaneously generates signals having extremely low frequencies Af andA12, which are sufficiently lower than that of the input of the phaseseparator (i.e., the musical sound signal having frequency f) and whichare 90 different in phase from each other; modular M and M which serveto amplitude-modulate the extremely low frequency signals (as carrierwaves) furnished from terminals d and e of the extremely low frequencyoscillator LFO with musical sound signals (as modulating waves)furnished from terminals b and c of the phase separator PS,respectively, and a high-pass filter F adapted to eliminate theextremely low frequency signal component (ie the carrier component) fromthe modulation output signal of each modulator. But, when balancedmodulators are employed for the modulators M and M the filter F is notrequired.

Now, it is assumed that a musical sound signal at the output terminal cof the phase separator lags by 90 than that at the terminal b in phaseand a carrier signal at the output terminal e of the extremely lowfrequency oscillator LFO also lags by 90 than that at the terminal d inphase, signals at terminals b, c, d, and e are represented by thefollowing formulas:

Terminal b a cos out (w Z'rrj) Terminal c a sin wt (to 2111) Terminal dA cosAwt (Awt= 21rAf) Terminal e A sinAmt (Amt ZrrAf) Therefore, whenthe signal at the terminal d is amplitude-modulated with the musicalsound signal at the terminal b in the modular M the resultant modulationoutput signal can be represented by the following formula:

M output A cosAwt (mA/2) {cos(m Aw)t cos(w Am)t} modulator M theresultant modulation output signal is represented by the followingformula:

M output A sinAwt (mA/2, {cos(m Am)t cos(w Aw)t} These M and M outputsignals are combined at the input terminal of the high-pass filter Finto a resultant signal represented by a formula shown below:

A (cosAwt sin Amt) mA cos Aw)! Awcomponent is removed by the high-passfilter F from this'combined signal, whereby a signal of a cos (a) Am)tis obtained at an output terminal k(1) of the filter F (A phase shiftdue to the filter is disregarded).

The signal thus obtained is a deviated musical sound signal (f Af) whichis lower by as much as the frequency Af of the extremely low frequencyoscillator LFO than the musical sound signal (f). Therefore, this iscorrespondent to Af of the frequency deviation device F8 shown in FIG 1.

Next, if the signals to be applied to the modulators M and Mrespectively through terminals 12 and c are interchanged with eachother, or the signals to be applied to the modulators M and Mrespectively through terminals d and e are interchanged with each other,a signal of b cos ((0 Aw)t is obtained at the output terminal of thehigh pass filter F. The signal thus obtained is a musical sound signal(f Af), the frequency of which is higher by as much as the frequency Afoscillated by the extremely low frequency oscillator than the frequency(f), and this is correspondent to -l-Af of the frequency deviationdevice FS shown in FiG. ll.

Therefore, when an oscillating frequency of the extremely low frequencyoscillator LFO in the frequency deviation device PS is Afl, and anoscillating frequency of the extremely low frequency oscillator LFO ofthe frequency deviation device FS: is Afg (but Afl a hf if a part of thesignal having the frequency (f-l- Af) obtained at the terminal k of thefrequency deviation device PS is fed to the input terminal j of thefrequency deviation device PS through the feed-back device F8 and in thesame way a part of the signal having the frequency (f Af obtained at theterminal I of the frequency deviation device PS is fed to the inputterminal i of the frequency deviation device FS, through the feedbackdevice FB signal represented by the following formulas are obtained atthe output terminals k and 1 respectively in the same way as mentionedbefore.

Terminal ka cos (m+A(o Aw )t Terminal lb cos (w+Aw Aw )t where a and [2represent respective amplitudes. Further, each of these output signalsis fed back to the input side of the other frequency deviation devicewhich is different from the frequency deviation device from which theoutput has come out, whereby signals a cos (w 2Am Aw )t and b cos ((0Am, 2Aw )t are obtained at the output terminals k and 1 respectively.Thus, a signal having a frequency spectrum as shown in FIG. 3 isobtained. These signals are fed to the output terminal m through'theresistors R and R and then are mixed with an original musical soundsignal furnished through the resistor R Then, the thus mixed signal isamplified properly and applied to a loudspeaker to produce a richtremolo sound effected intricately by amplitude modulation, frequencymodulation or phase modulation.

In the above description, the frequency characteristic of the feed-backdevices FB and F8 has not been explained. However, if the frequencycharacteristic of these said devices is made to have specially greatattenuation in the low frequency regions, the envelope of a highfrequency spectrum will be relatively widened in respect of the overallcharacteristic. This is more effective for a sound which is rich inhigher harmonics as found in a musical string instrument. It is possibleto select feed-back devices having various characteristics other thandescribed above in order to obtain various effects on sound.

The above description relates to only such a case wherein the frequencydeviation devices PS and PS cause respectively a frequency deviation of+Af and Af However, if :Af and Mf are adopted as frequency deviations byutilizing two side band modulation devices, signals obtained at theterminals k and l are respectively a, cos ((0 :tAwQt +a cos (w :Aw i Aw)t +11 cos (w i 2Aw i Aw )t and b cos ((0 :t Aw )t +b cos(w i- Aw i Aw)t +b cos (w i 2A1 2*: A0 As a result, a multiple tremolo effect soundmore intricate than the ones described above can be obtained.

In an example shown in FIG 4, a feed-back device FB similar to thatshown in FIG 1 is connected between the input side and the output sideof a frequency deviation device FS and in the same way a feedback deviceFB is connected between the input side and the output side of afrequency deviation device PS Therefore, when two frequency deviationdevices F S and PS having frequency deviations +Af and Af respectivelyare employed, the frequencies of output signals obtained at the outputterminals k and l are (f Afr) and (f Af respectively. When a part ofeach output signal mentioned above is fed back to its respective inputterminal 1' or j through its respective feedback device FB or F8 signalsrepresented by the following formulas are obtained at the outputterminals k and 1 respectively in the same way as in the case of FIG. 1:

Terminal k a cos 2Aw )t Terminal I 12 cos (0) Aw )t These signals arefed back tothe input sides respectively, and the signals of a cos (w 3Aw)t and b cos (0: 3Am )t are obtained at the output sides respectively.By repeating the feed-back operation in the sameway, signals representedby the following general formulas can be obtained.

. n Terminal k 2 a; cos (w-i-iAwQt 11 Terminal Z 2 b cos (w-t'AwQt wherea, and b are signal amplitudes.

As shown in FIG. 5, the frequency spectrum of these signals shows manyfrequencies (side band frequency) spread at the intervals of Af and Afon the both sides of the musical sound frequency (f). These signals arefed to the output terminal m through resistors R and R and then aremixed with an original musical sound signal furnished through a resistorR thereby to obtain a signal represented by a formula below:

where B is the amplitude. This signal is obtained by combining thesignal which frequency is (f) and a signal which is deviated by as muchas Af or Afi on the both sides of the frequency (1). Therefore, themusical sound signal can be considered as a multi-rank sound consistingof a multi-sound source. Moreover, to this signal the effects ofamplitude-modulation and phase modulation are added, whereby anintricate tremolo effect can be obtained.

In the above description, the frequency characteristics of the feed-backdevices FB and FE, are not explained. However, if the frequencycharacteristic is made to have specially great attenuation in the lowfrequency components, the envelope of a high frequency spectrum will bewidened in respect of the overall characteristic. This is more effectivefor a sound which is rich in higher harmonics as found in a stringmusical instrument. It is possible to select feed-back devices havingvarious characteristics other than described above, in order to obtainvarious effects on sound.

In the above description, M1 is not equal to Af However, if Af, and Af,are such in valve that if one is an integral multiple of the other, highfrequencies arranged thereby to reduce the effect on sound. Therefore,it is desirable to so select the values of Af and Af that one is not anintegral multiple of the other.

Further, it is explained in the above description that the musical soundsignal frequency is deviated either higher or lower by as much as theextremely low frequency Af, or Af in the respective frequency deviationdevices FS, and F 8,. However, it is possible to simultaneously deviatethe frequency higher and lower by as much as Afl, or Af by employing atwo side band modulation. The frequency spectrum of the output signal inthis case becomes much more intricate than that in FIG. 5. As a result,a much higher tremolo effect can be obtained.

While a few embodiments of the present invention have been illustratedand described in detail, it is particularly understood that theinvention is not limited thereto or thereby.

I claim:

1. An electronic tremolo effect producing device which comprises: amusical sound signal circuit generating a musical sound signal; a firstfrequency deviation means connected to said musical sound signal circuitfor deviating the frequency of said musical sound signal frequency by asmuch as a first deviation frequency sufficiently lower than thefrequency of said musical sound signal; a second frequency deviationmeans connected to said musical sound signal circuit for deviating thefrequency of said musical sound signal frequency by as much as a seconddeviation frequency which is sufficiently lower than the frequency ofsaid musical sound signal and is different from said first deviationfrequency; a first feed-back means connected to feed back a part of theoutput of said first frequency deviation device to an input side of saidsecond frequency deviation means; and a second feed-back means connectedto feed back a part of the output of said second frequency deviationmeans to an input side of said first frequency deviation means, outputsignals from said first frequency deviation means and said secondfrequency deviation means being combined with said musical sound signalthereby to obtain a tremolo effect signal.

1. An electronic tremolo effect producing device which comprises: amusical sound signal circuit generating a musical sound signal; a firstfrequency deviation means connected to said musical sound signal circuitfor deviating the frequency of said musical sound signal frequency by asmuch as a first deviation frequency sufficiently lower than thefrequency of said musical sound signal; a second frequency deviationmeans connected to said musical sound signal circuit for deviating thefrequency of said musical sound signal frequency by as much as a seconddeviation frequency which is sufficiently lower than the frequency ofsaid musical sound signal and is different from said first deviationfrequency; a first feed-back means connected to feed back a part of theoutput of said first frequency deviation device to an input side of saidsecond frequency deviation means; and a second feed-back means connectedto feed back a part of the output of said second frequency deviationmeans to an input side of said first frequency deviation means, outputsignals from said first frequency deviation means and said secondfrequency deviation means being combined with said musical sound signalthereby to obtain a tremolo effect signal.